JP4150605B2 - Polarizer - Google Patents

Description

【００６１】
１−４：セルロースアシレートフィルムの鹸化
下記のいずれかの方法で鹸化を行い、表１に記載した。
（ｉ）塗布鹸化
・ｉｓｏ-プロパノール８０質量部に水２０質量部を加え、これにＫＯＨを１．５規定となるように溶解し、これを２０℃に調温したものを鹸化液として用いた。
・これを２０℃のセルロースアシレートフィルム上に塗布し、表１記載の時間処理し、鹸化深さを調整した。
・この後、水洗法あるいは中和法（表１に記載）の方法で洗浄を行った。
水洗法：５０℃の温水をスプレーを用い、１０ｌ／ｍ²・分で１分間吹きかける。
中和法：２５℃の０．５Ｎの硫酸の浴に３０秒浸漬後、２５℃の水の浴に３０秒浸漬する。
（ii）浸漬鹸化
・ＮａＯＨの１．５規定水溶液を鹸化液として用いた。
・これを２５℃に調温し、セルロースアシレートフィルムを表１記載の時間浸漬し、鹸化深さを調整した。
・この後、塗布鹸化法と同様に、水洗法あるいは中和法（表１に記載）で洗浄を行った。
【００６２】
このようにして得た鹸化サンプルの鹸化深さ、表面の残留酸量は以下の方法で測定した。
＜鹸化深さ測定法＞
・ミクロトームを用い、セルロースアシレートフィルムを斜め４５度の角度で厚み２μｍの切片を作成する。
・これを顕微ＩＲを用い、５μｍ×２０μｍのアパーチャーで表面から２μｍ毎に測定する（最表面はアパーチャーの２０μｍの辺と切片の最表面とを合わせて測定する）。
・１７００〜１８００ｃｍ^-1に現れる最大吸光度（Ａ１）と１１００〜１０００ｃｍ^-1に現れる最大吸光度（Ａ２）の比率をとり（Ａ１／Ａ２）を求める。Ａ１はアシル基のカルボニル基に起因し、Ａ２はアシル基のカルボニル基とグルコピラノース環のエーテル結合の両者に起因し、この比が減少するほど鹸化が進行したことを意味する。
・横軸に測定深さ（表面からＸステップの測定点の深さは、２Ｘ／（ｓｉｎ４５°）で表され、最表面をＸ＝１とする）、縦軸にＡ１／Ａ２をとり、これをプロットする。
・Ａ１／Ａ２が１．５以下の領域を鹸化深さとした。
＜残留酸量＞
・鹸化表面をＸＰＳ（島津製作所製ＥＳＣＡ−７５０型）で測定し、洗浄に使用した酸に起因するＳ２ｐのシグナルを測定した。
・このピークの面積をＣのピークの面積で割り、さらにこのＳ２ｐのピークのイオン化断面積で割った値を百分率で表したものを残留した酸量とした。
【００６３】
２．偏光板の作成
２−１：偏光層の作成
下記方法のいずれか（表２に記載）厚み２０μｍの偏光層を調製した。
（ｉ）斜め延伸法
ＰＶＡフィルム（クラレ製９Ｘ７５ＳＲ）を下記組成の染色液に２５℃にて９０秒浸漬した。
＜染色液＞
ヨウ素 １．０質量部
ヨウ化カリウム ６０．０質量部
水 １０００質量部
これに下記組成の硬膜液のいずれか（表２に記載）に２５℃にて１２０秒浸漬し、硼酸の初期含有率の異なるものを作成した。
＜硬膜液−１＞
ホウ酸 ４０質量部
ヨウ化カリウム ３０質量部
水 １０００質量部
＜硬膜液−２＞
ホウ酸 ８０質量部
ヨウ化カリウム ６０質量部
水 １０００質量部
＜硬膜液−３＞
ホウ酸 １２０質量部
ヨウ化カリウム ９０質量部
水 １０００質量部
この後、特開平２００２−８６５５４号公報の実施例１に従い、テンターを用い延伸軸が斜め４５度となるように延伸した。なお、延伸は６０℃９５％ＲＨにおいて７倍に延伸した後、５．３倍まで収縮させた。この後、７０℃で２分間乾燥させた。
【００６４】
（ii）平行延伸法
特開平２００１−１４１９２６号公報の実施例１に準じ、ＰＶＡフィルム（クラレ製９Ｘ７５ＳＲ）を上記染色液に３０℃で浸漬しながら、２対のニップロール間に周速差を与え、長手方向に３倍に延伸した。
これをさらに上記硬膜液に浸漬し６０℃で、６．５倍（未延伸フィルムに対する倍率）に２対のニップロールを用い延伸した。これを５０℃で５分間乾燥させた。
【００６５】
２−２：貼り合わせ
このようにして得た偏光板と、上記鹸化処理したセルロースアシレートフィルムを、ＰＶＡ（（株）クラレ製ＰＶＡ−１１７Ｈ）３％水溶液を接着剤として貼り合わせ、さらに６０℃で３０分間加熱して偏光板を作成した。なお、貼り合わせは、偏光軸と、セルロースアシレートフィルムの長手方向が４５度となるように張り合わせた。
【００６６】
３．偏光板の評価
上記偏光板を粘着剤を用いてガラス板の両面に偏光軸が直行するように貼り付けた。これを、６０℃９５％ＲＨで１０００時間サーモ経時させた。
これの全光透過率を測定し、偏光能を評価した。さらに、このサーモ処理前、後の偏光板から偏光層を取り出し、上記方法で硼素量を測定した。さらに、この比からサーモ処理に伴う硼素量の変化率とした。さらに、サーモ処理後の偏光板から上記方法で偏光層中の硼素のＮＭＲを測定し、０ｐｐｍと１０ｐｐｍの強度比を求めた。これらの値を表２に記載した。
また、接着性は、６０℃９５％ＲＨでの１０００時間サーモ処理後に、３ｍｍごとに偏光層に縦、横に１０本ずつ剃刀で切れ目を入れ、これに粘着テープを貼り付け、これを素早く剥ぎ取り、剥ぎ取られなかった偏光層の面積（％）を目視評価した。結果を表２に示した。
【００６７】
【表２】

【００６８】
本発明の偏光板は、極めて堅牢な耐久性を達成し、６０℃９５％ＲＨでの１０００時間サーモ処理は言うに及ばず、さらに条件の厳しい７０℃９５％ＲＨサーモ条件でも良好な結果を得た。
また、本発明の偏光板では、サーモ耐久性達成のためセルロースアシレートフィルムの鹸化処理深さを浅くしたが、Ｍｇ、Ｃａ含量を低くすることで、いずれも良好な接着性を達成した。
【００６９】
４．偏光板の表示素子への応用
本発明の偏光板を、特開平１０−４８４２０号公報の実施例１に記載の液晶表示装置、特開平９−２６５７２号公報の実施例１に記載のディスコティック液晶分子を含む光学的異方性層、ポリビニルアルコールを塗布した配向膜、特開２０００−１５４２６１号公報の図２〜９に記載のＶＡ型液晶表示装置、特開２０００−１５４２６１号公報の図１０〜１５に記載のＯＣＢ型液晶表示装置に用いたところ良好な性能が得られた。
【００７０】
【発明の効果】
本発明により、極めて過酷な湿熱条件においても耐久性に優れる偏光板を提供することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polarizing plate having excellent temporal stability.
[0002]
[Prior art]
In general, a polarizing plate has a protective film bonded to both sides or one side of a polarizing layer having polarizing ability via an adhesive layer. As a material for the polarizing layer, polyvinyl alcohol (hereinafter referred to as PVA) is mainly used. After the PVA film is uniaxially stretched, it is dyed with iodine or a dichroic dye or dyed, and then stretched. A polarizing film for a polarizing layer is formed by crosslinking with a compound. As the protective film, cellulose triacetate (TAC) is mainly used because it is optically transparent and has a small birefringence.
However, if such a polarizing plate is left in a high-temperature and high-humidity atmosphere, there has been a problem that the polarization characteristics deteriorate over time. This is because PVA having a large water absorption is used for the polarizing layer, so that the orientation of the PVA molecules stretched by moisture absorption is disturbed, and the orientation and adsorption of iodine that is oriented and adsorbed along this are disturbed. It was thought to decrease. Furthermore, the cellulose acetate film often used for the protective film has high moisture permeability, and easily promotes disturbing the orientation of the PVA. On the other hand, these failures are unlikely to occur under low humidity, and no significant change appears at 90 ° C. That is, if PVA does not swell under high humidity, these failures are unlikely to occur.
[0003]
As a countermeasure against such deterioration in polarizing plate characteristics under high humidity, Patent Document 1 (Japanese Patent Application Laid-Open No. 2001-116922) describes the improvement of the stretching conditions of the PVA polarizing layer and the moist heat resistance of the orientation of PVA and iodine. A method for improving and suppressing the deterioration of polarization characteristics is described. That is, focusing on the fact that the decrease in polarization is iodine desorption, we have developed a stretching method in which this is unlikely to occur. However, this method can improve the resistance after 500 hours in a 60 ° C. and 90% RH atmosphere, but the resistance after 1000 hours in a more severe 60 ° C. and 95% RH atmosphere is insufficient. There is a slight difference of 5% RH between 60 ° C. 90% RH and 60 ° C. 95% RH, but the water absorption rate of PVA is about 30% higher than the former, which is a very severe condition.
[0004]
Furthermore, Patent Document 2 (Japanese Patent Laid-Open No. 2002-90546) describes that a norbornene-based film having a small water vapor permeability is used as a protective film for a polarizing plate. However, such a hydrophobic polymer has poor adhesion to hydrophilic PVA, and film peeling is likely to occur after a long period of use, and accordingly, polarization characteristics are liable to be lowered. In addition, since such norbornene-based films are more fragile than TAC, scraps are easily generated at the time of cutting, which is inferior in processability and expensive.
Patent Document 3 (Japanese Patent Laid-Open No. 2002-55227) discloses that the entire surface of a polarizing plate is covered with a layer having a low moisture permeability, but this method complicates the manufacturing process and is not practical. It was.
[0005]
[Patent Document 1]
JP 2001-116922 A
[Patent Document 2]
JP 2002-90546 A
[Patent Document 3]
JP 2002-55227 A
[0006]
[Problems to be solved by the invention]
An object of the present invention is to provide a polarizing plate excellent in durability even under extremely severe wet heat conditions.
[0007]
[Means for Solving the Problems]
1. A method for producing a polarizing plate comprising a cellulose acylate film and a polarizing layer containing polyvinyl alcohol, iodine and boric acid,
The cellulose acylate film was subjected to alkali saponification treatment, washed only with water, bonded to the polarizing layer, and after 1000 hours in an atmosphere of 60 ° C. and 95% RH, the boron content in the polarizing layer was 79% of the initial value. The manufacturing method of the polarizing plate characterized by preparing the polarizing plate of 100% or less above.
2. After 1000 hours in an atmosphere of 60 ° C. and 95% RH, the boron content in the polarizing layer is 2 mmol / m. ² ・ Μm or more 20mmol / m ² -The manufacturing method of the polarizing plate of said 1 characterized by being below micrometer.
3. The ratio of the peak intensity of 0 ppm to the peak of 12 ppm (peak height of 0 ppm / peak height of 12 ppm) is 2 or more when NMR measurement is performed on boron in the polarizing layer after 1000 hours in an atmosphere of 60 ° C. and 95% RH. 3. The method for producing a polarizing plate according to 1 or 2 above, which is 40 or less.
4). 4. The method for producing a polarizing plate according to any one of 1 to 3, wherein the washing is performed by spraying warm water of 40 ° C. or higher in a spray form.
5. 5. The method for producing a polarizing plate according to 4 above, wherein the cellulose acylate film has a substitution degree of an acyl group substituted with a hydroxyl group at the 6-position of cellulose of 0.87 or more and 0.95 or less.
6). The cellulose acylate film is at least selected from ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, and esters having 3 to 12 carbon atoms, which are non-chlorine organic solvents. 6. The method for producing a polarizing plate according to 4 or 5 above, wherein the film is formed by a solution casting method using a kind of solvent.
7). 7. The method for producing a polarizing plate according to any one of 1 to 6 above, wherein the polarizing layer is stretched by a tenter with the absorption axis substantially inclined by 45 degrees.
8). 8. The method for producing a polarizing plate according to any one of 1 to 7 above, wherein the washing is performed so that the film surface pH is 5 to 9.
9. 9. The method for producing a polarizing plate according to any one of 1 to 8 above, wherein a saponification solution in which the alkali saponification treatment is adjusted to 10 to 30 ° C. is used, and the reaction time is 1 second to 5 minutes. .
10. 10. The method for producing a polarizing plate according to 9 above, wherein the alkali saponification treatment is performed using a saponification solution adjusted to 10 to 25 ° C.
  According to this invention, the polarizing plate of the following structure is provided and the said objective of this invention is achieved. Furthermore, the circularly-polarizing plate and liquid crystal display device using the polarizing plate of the following structure are provided.
  1. After 1000 hours of aging at 60 ° C. and 95% RH, the boron content in the polarizing layer is the initial value.79A polarizing plate, characterized by being from 100% to 100%.
  2. The content of boron in the polarizing layer is 2 mmol / m after 1000 hours in an atmosphere of 60 ° C. and 95% RH.²・ Μm or more 20mmol / m²-The polarizing plate of said 1 characterized by being below micrometer.
  3. The ratio of the peak intensity of 0 ppm to the peak of 12 ppm (the peak height of 0 ppm / the peak height of 12 ppm) was measured by NMR for boron in the polarizing layer after 1000 hours in an atmosphere of 60 ° C. and 95% RH. 2 or more and 40 or less, The polarizing plate of said 1 or 2 characterized by the above-mentioned.
  4). 4. The polarizing plate according to any one of 1 to 3, wherein the polarizing plate is formed of at least one cellulose acylate film and a polarizing layer comprising at least polyvinyl alcohol, iodine and boric acid.
  5. Cellulose acylate film is a hydroxyl group at the 6-position of celluloseOf the acyl group substituted byThe degree of substitution is 0.87 or more and 0.95 or less.the above4. The polarizing plate according to 4.
  6). The cellulose acylate film is at least selected from ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, and esters having 3 to 12 carbon atoms, which are non-chlorine organic solvents. 6. The polarizing plate as described in 4 or 5 above, which is formed by a solution casting method using a kind of solvent.
  7. 7. The polarizing plate as described in any one of 1 to 6 above, wherein the polarizing axis is stretched by a tenter with the absorption axis of the polarizing layer inclined substantially 45 degrees.
  8). Cellulose acylate film is a hydroxyl group of celluloseOf the acyl group substituted byThe polarizing plate as described in any one of 4 to 7 above, which comprises a single or mixture of cellulose acylates satisfying all of the following formulas (I) to (III).
    Formula (I): 2.6 ≦ SA + SB ≦ 3.0
    Formula (II): 2.0 ≦ SA ≦ 3.0
    Formula (III): 0 ≦ SB ≦ 0.8
    Formula (IV): 280 ≦ degree of polymerization ≦ 380
(In the formula, SA and SB represent the substitution degree of the acyl group substituted by the hydroxyl group of cellulose, SA is the substitution degree of the acetyl group, and SB is the substitution degree of the acyl group having 3 to 22 carbon atoms. )
  9. The polarizing plate according to any one of 4 to 8, wherein the cellulose acylate film is cast into a film after being dissolved in a solvent formed substantially from a non-chlorine solvent.
  10. The circularly-polarizing plate or liquid crystal display element using the polarizing plate of said 1-9.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
The present invention has newly found out that in order to greatly improve the heat and humidity resistance of a polarizing plate, it is important to suppress the desorption of iodine in the polarizing layer by suppressing the dissipation of boric acid and the change in coordination number. based on. In the present invention, a layer exhibiting polarizing ability (a layer in which a pigment and polyvinyl alcohol are stretched is called a polarizing layer, and a laminate of at least one protective film (cellulose acylate film) is called a polarizing plate. Distinguish between the two.
The polarizing layer achieves polarization ability by adsorbing iodine to PVA and stretching it, and arranging iodine along PVA. Conventionally, in order to improve the heat-and-moisture resistance of a polarizing plate, it has been carried out mainly to prevent such element dissipation, but there has been no drastic method. In this invention, the point which paid its attention to the boric acid and borax added in order to bridge | crosslink PVA is a new idea. That is, the PVA molecules are aligned in parallel by stretching, and the iodine is oriented between them, but in order to prevent the dissipated oriented iodine, the point of the present invention is not to reduce the cross-linking of boric acid and borax. is there. In the presence of cross-linking, iodine is fixed in a very rigid space and cannot be dissipated. This is because iodine is firmly fixed in a ladder-like space because boric acid and borax are cross-linked between PVA molecules arranged in parallel by stretching. On the other hand, when the cross-linking by boric acid / borax is reduced, PVA can move freely under high humidity, so iodine is easily dissipated. Dissipation of iodine cannot be prevented by the conventional method of improving the orientation of PVA by devising the stretching method.
[0009]
In order to maintain the cross-linking of boric acid and borax, the content of boron in the polarizing layer after aging for 1000 hours in an atmosphere of 60 ° C. and 95% RH is preferably 40% or more and 100% or less, more preferably 50% or more. 100% or less, more preferably 60% or more and 100% or less. Thereby, the reduction | decrease in the number of bridge | crosslinking points can be suppressed.
Further, the content of boron in the polarizing layer after aging at 60 ° C. and 95% RH for 1000 hours is 2 mmol / m²・ Μm or more 20mmol / m²-It is preferable that it is below μm, more preferably 2.5 mmol / m²・ Μm or more 15mmol / m².Mu.m or less, more preferably 3 mmol / m²・ Μm or more 10mmol / m²-It is below μm. This value is unit area (1m²), The amount of boron in the polarizing layer per unit thickness (1 μm).
Furthermore, when the NMR measurement is performed on boron in the polarizing layer after 1000 hours of 60 ° C. and 95% RH, the ratio of the peak intensity of 0 ppm to the peak of 12 ppm is preferably 2 or more and 40 or less, more preferably 2 or more and 30 or less. More preferably, it is 2 or more and 20 or less. The 12 ppm peak corresponds to tricoordinate boric acid and the 0 ppm peak corresponds to 4 ranges of boron. That is, the larger this ratio (0 ppm peak height / 12 ppm peak height), the more tetracoordinate boric acid. In the case of tetracoordinate boric acid, after stretching, the two PVA chains are cross-linked through a hydroxyl group and boric acid to form a ladder and are fixed. And the element which exists between two PVA chains does not dissipate. In the case of tricoordinate boric acid, in the case of tetracoordinate boric acid, the space between the two PVA chains fixed by cross-linking spreads, and the element existing between them is dissipated. Thus, it is important to keep boric acid tetracoordinated.
[0010]
Such an existing state of boric acid can be expressed by the following methods (1) and (2).
(1) Method for reducing the number of hydroxyl groups that react with boric acid in cellulose acylate
(2) Method for adjusting the amount of acid remaining on the surface of the cellulose acylate film to 0% or more and 1% or less
[0011]
First, the method (1) will be described.
Usually, boric acid and borax are coordinated to the hydroxyl group of polyvinyl alcohol (PVA) in the polarizing layer, but this coordination is removed under high humidity and diffuses from the PVA layer to the protective layer made of cellulose acylate. At this time, if there is a hydroxyl group in the cellulose acylate layer, it is coordinated and fixed thereto. As a result, boron in the polarizing layer is reduced. Therefore, it is necessary to reduce the hydroxyl groups in cellulose acylate.
On the other hand, the hydroxyl group of cellulose acylate includes a hydroxyl group that is reactive with boric acid inherent in cellulose acylate and a hydroxyl group associated with the saponification treatment of the cellulose acylate surface performed to improve the adhesion to the polarizing layer. There are types. By reducing these hydroxyl groups, the hydroxyl groups in cellulose acylate can be reduced. Either of these two kinds of hydroxyl groups may be reduced, but a synergistic effect can be obtained by reducing both of them together.
[0012]
(I) Method for reducing hydroxyl groups reactive with boric acid inherent in cellulose acylate
Cellulose acylate is obtained by substituting the hydroxyl groups at positions 2, 3, and 6 of the glucopyranose ring with an acylate group. If all three hydroxyl groups are substituted, the solubility is lowered, so that solution casting cannot be performed. For this reason, the degree of substitution is generally 2.7 to 2.9. For this reason, there are 0.1-0.3 hydroxyl groups per glucopyranose ring, which react with boric acid. Of these three hydroxyl groups, the hydroxyl group at the 6-position has the highest reactivity with boric acid. Since the hydroxyl group at the 6-position is bonded via a methylene group from the glucopyranose ring, the mobility is large and the reactivity is high. On the other hand, the hydroxyl groups at the 2- and 3-positions are directly bonded to the glucopyranose ring and the hydrogen bonds between the hydroxyl groups at the 2- and 3-positions, so that the reactivity is low and the reactivity with boric acid is low.
For this reason, in this invention, it is preferable to reduce this 6-position hydroxyl group. Specifically, the substitution degree at the 6-position (S6) is preferably 0.87 to 0.97, more preferably 0.88 to 0.96, and still more preferably 0.89 to 0.95. It is as follows. Incidentally, the substitution rate of the hydroxyl group at the 6-position of normal cellulose acylate is 0.7 to 0.8. In order to achieve such a cellulose acylate having a high 6-position substitution rate, the following method is used.
[0013]
The basic principle of the cellulose acylate synthesis method is described in Mita et al., Wood Chemistry pages 180-190 (Kyoritsu Shuppan, 1968). A typical synthesis method is a liquid phase acetylation method using an acetic anhydride-acetic acid-sulfuric acid catalyst. Specifically, a cellulose raw material such as wood pulp is pretreated with an appropriate amount of an organic acid, and then it is esterified by adding it to a pre-cooled acylated mixture to complete cellulose acylate (2nd, 3rd and 6th positions). The total degree of acyl substitution is approximately 3.00). The acylated mixed solution generally contains an organic acid as a solvent, an anhydrous organic acid as an esterifying agent, and sulfuric acid as a catalyst. The organic acid anhydride is usually used in a stoichiometric excess over the sum of the cellulose that reacts with it and the water present in the system. After completion of the acylation reaction, a neutralizing agent (for example, calcium, magnesium, iron, aluminum or zinc) is used for hydrolysis of excess organic anhydride remaining in the system and neutralization of a part of the esterification catalyst. Of carbonate, acetate or oxide). Next, the obtained complete cellulose acylate is saponified and aged by maintaining it at 50 to 90 ° C. in the presence of a small amount of an acetylation reaction catalyst (generally, remaining sulfuric acid), and the desired acyl substitution degree and The cellulose acylate having a polymerization degree is changed. When the desired cellulose acylate is obtained, the catalyst remaining in the system is completely neutralized with the neutralizing agent as described above, or water or dilute sulfuric acid without neutralization. The cellulose acylate solution is charged into the inside (or water or dilute sulfuric acid is added into the cellulose acylate solution) to separate the cellulose acylate, and the cellulose acylate is obtained by washing and stabilizing treatment.
[0014]
In an ordinary cellulose acylate synthesis method, the acyl substitution degree at the 2-position or the 3-position is higher than the acyl substitution degree at the 6-position. Therefore, in order to obtain the cellulose acylate described above, it is necessary to specifically adjust the above reaction conditions. As specific reaction conditions, it is preferable to reduce the amount of the sulfuric acid catalyst and lengthen (ripen) the acylation reaction time. When the amount of the sulfuric acid catalyst is large, the acylation reaction proceeds faster, but a sulfuric ester is formed between the cellulose and the cellulose according to the amount of the catalyst, and is released at the end of the reaction to form a residual hydroxyl group. Sulfate esters are more produced at the 6-position, which is highly reactive. Therefore, when there is much sulfuric acid catalyst, the acyl substitution degree of 6-position will become small. Therefore, in order to synthesize the cellulose acylate used in the present invention, it can be obtained by reducing the amount of sulfuric acid catalyst as much as possible and extending the reaction time in order to compensate for the lowered reaction rate. In addition, control of the 2-position substitution degree and 3-position substitution degree in the present invention is also possible by changing the reaction conditions.
[0015]
(B) Reduction method of hydroxyl group generation due to saponification treatment of cellulose acylate surface to improve adhesion to polarizing layer
The cellulose acylate film is hydrophobic, and as it is, it does not adhere to the hydrophilic polarizing layer mainly composed of PVA. For this reason, in order to increase the hydrophilicity of the surface, saponification of the surface of the cellulose acylate film is generally performed.
In saponification, cellulose acylate is treated with an acid or alkali solution, and the acylate ester of the cellulose acylate film is hydrolyzed (saponified) to generate hydroxyl groups on the surface. By such treatment, the surface of about 5 μm to 10 μm is hydrolyzed to cellulose. Since such a saponified surface has a high concentration of hydroxyl groups, the thickness is thin, but almost all acylate groups are hydrolyzed. Therefore, hydroxyl groups that are equal to or more than the hydroxyl groups remaining in the whole cellulose acylate in (a) above are saponified. Present in the layer.
Therefore, in the present invention, the thickness of the saponified layer is preferably 0.1 μm or more and 3 μm or less, more preferably 0.2 μm or more and 2 μm or less, and further preferably 0.3 μm or more and 1.5 μm or less. In this way, the formation of hydroxyl groups can be reduced.
Such a saponification treatment can be achieved by the following method.
Any saponification solution may be used as long as cellulose acylate is hydrolyzed, and an acid or alkali solution is used for this. More preferred is an alkaline solution, and sodium hydroxide, potassium hydroxide, ammonia and the like are more preferably used. The solvent is not particularly limited, and may be either water-based or organic solvent-based. More preferred are aqueous and alcoholic solvents. The aqueous system refers to a water content of 50% by mass or more, and may contain a solvent having good compatibility with water such as alcohol in addition to water. The alcohol type refers to an alcohol content of 50% by mass or more, and may contain a solvent having good compatibility with alcohol such as water in addition to alcohol. The alcohol solvent is preferably an alcohol having 1 to 5 carbon atoms, more preferably methanol, ethanol or propanol, and still more preferably iso-propanol.
The pH of the saponification coating solution is preferably 10 or more, more preferably 12 or more. The specified concentration of hydroxide ions is preferably 0.1N to 3.0N, more preferably 0.5N to 2.0N.
The saponification treatment may be immersed in a saponification solution or an alkali solution may be applied. In order to precisely control the depth of the saponification treatment as in the present invention, it is more preferable to carry out by a coating method. In the case of the coating method, an organic solvent-based coating solution that can be uniformly coated (no repelling) is more preferably used, and in the case of the coating method, an aqueous coating solution is more preferably used.
[0016]
(B-1) Coating saponification
In this method, saponification is performed by a coating method. In this case, examples of the coating method include a dip coating method, a curtain coating method, an extrusion coating method, a bar coating method, a spray method, and an E-type coating method. The solvent of the alkali saponification coating solution has good wettability because it is applied to the transparent support of the saponification solution, and the surface state remains good without forming irregularities on the surface of the transparent support by the saponification solution solvent. It is preferred to select a solvent to keep. Achieving the above depth can be controlled by liquid temperature and time. The reaction temperature is usually 50 to 80 ° C., but in the present invention, it is preferably 10 to 30 ° C. in order to reduce the saponification depth. More preferably, it is 15 ° C. or higher and 25 ° C. or lower. The reaction time is preferably 1 second to 5 minutes at room temperature, more preferably 5 seconds to 5 minutes, and particularly preferably 20 seconds to 3 minutes.
After applying the saponification solution, it is common to apply and neutralize an acidic aqueous solution of 0.01N to 3.0N hydrochloric acid, nitric acid, sulfuric acid, acetic acid, formic acid, chloroacetic acid, oxalic acid, etc. Then, it is preferable not to perform this neutralization process and to wash with water. That is, it is sufficiently washed so that the film surface pH is 5 to 9 (the film surface pH can be measured by bringing a flat glass pH electrode into contact with the film surface). Such washing with water may be applied with water or sprayed. Thereby, the amount of residual acid on the surface described below can be achieved.
[0017]
(B-2) Immersion saponification
The saponification treatment is performed by immersing the cellulose acylate film in an alkaline solution. The temperature of the alkaline solution is generally 50 to 80 ° C., but in the present invention, it is preferably 10 to 30 ° C. in order to reduce the saponification depth. More preferably, it is 15 degreeC-25 degreeC. The immersion time is usually 3 to 5 minutes, but in the present invention it is 2 minutes or less, more preferably 1.5 minutes or less.
[0018]
As described above, the thickness of the saponification layer is reduced by any of the coating method and the dipping method, but this reduces the adhesion between the polarizing layer and the cellulose acylate. In the present invention, the adhesion is improved by the following method. That is, in the present invention, the polyvalent metal ions such as Mg and Ca in the cellulose acylate are adjusted to 100 ppm or less.
Adhesiveness is manifested by hydrogen bonds between the PVA of the polarizing layer and the hydroxyl groups of cellulose acylate. However, when multivalent ions are present here, these hydrogen bonds are broken and the adhesiveness is likely to be lowered. For this reason, in the present invention, a saponified layer having a high adhesiveness is formed even if it is thin by reducing the number of multivalent ions. Such cellulose acylate with less multivalent ions can be obtained by increasing the washing temperature in the final cellulose acylate production process. In general, washing is performed at room temperature, but in the present invention, washing is performed with water at 50 ° C. or higher, preferably 60 ° C. or higher. The quantification of the metal polyvalent ions can be determined by wet ashing cellulose acylate in nitric acid and measuring it by atomic absorption method or ICP-MS method.
[0019]
(2) The amount of acid remaining on the surface of the cellulose acylate film is 0% or more and 1% or less.
Boric acid proceeds using an acid as a catalyst when reacting with a hydroxyl group. A particularly strong catalyst is sulfuric acid. As described above, the surface of cellulose acylate is saponified to improve adhesion. At that time, after saponifying with alkali, neutralizing with acid such as sulfuric acid is a conventional general method. is there. At this time, if the acid remains, the reaction between boric acid and cellulose acylate is accelerated.
In this method of the present invention, after alkaline saponification treatment, only water washing is performed. Conventionally, after washing with water, neutralization treatment is performed by passing an acidic aqueous solution of 0.01N to 3.0N hydrochloric acid, nitric acid, sulfuric acid, acetic acid, formic acid, chloroacetic acid, oxalic acid, etc. preferable. In the present invention, in order to achieve a sufficient cleaning effect only by washing with water, hot water of 40 ° C. or higher is sprayed on the surface of the water to completely wash away the alkali and do not leave it. As a measure of cleaning, it is preferable to sufficiently clean the film so that the pH of the film surface is 5-9.
The amount of acid remaining can be measured using XPS. That is, paying attention to the elements contained in the used acid, XPS is measured, each peak is divided by the ionization cross section, and the peak intensity ratio with respect to carbon is shown in%. This is preferably from 0% to 1%, more preferably from 0% to 0.5%, and even more preferably from 0% to 0.1%.
The ionization cross section indicates the number of photoelectrons that are detected when the same number of elements are present. Therefore, by dividing the signal intensity (number of photoelectrons) measured by XPS by this value, the molar ratio of each element can be obtained.
[0020]
  The present invention will be described in detail below in order according to the manufacturing process.
1. Cellulose acylate
  Preferred cellulose acylates of the present invention can include the following materials. That is, the 6th position of cellulose acylateAcyl groupThe degree of substitution (S6) is preferably from 0.87 to 0.95. Furthermore, what satisfies all of the following formulas (I) to (IV) is more preferable.
  Formula (I): 2.6 ≦ SA + SB ≦ 3.0
  Formula (II): 2.0 ≦ SA ≦ 3.0
  Formula (III): 0 ≦ SB ≦ 0.8
  Formula (IV): 280 ≦ degree of polymerization ≦ 380
  In the formula, SA and SB represent the substitution degree of the acyl group substituted by the hydroxyl group of cellulose, SA is the substitution degree of the acetyl group, and SB is the substitution degree of the acyl group having 3 to 22 carbon atoms.
  Glucose units having β-1,4 bonds constituting cellulose have free hydroxyl groups at the 2nd, 3rd and 6th positions. Cellulose acylate is a polymer obtained by esterifying some or all of these hydroxyl groups with acyl groups. The degree of acyl substitution means the proportion of cellulose esterified at each of the 2-position, 3-position and 6-position (100% esterification has a degree of substitution of 1).
  The acyl group (SB) having 3 to 22 carbon atoms of the cellulose acylate of the present invention may be an aliphatic group or an allyl group, and is not particularly limited. These are, for example, cellulose alkylcarbonyl esters, alkenylcarbonyl esters, aromatic carbonyl esters, aromatic alkylcarbonyl esters, and the like, each of which may further have a substituted group. Among these, preferred acyl groups include propionyl, butanoyl, keptanoyl, hexanoyl, octanoyl, decanoyl, dodecanoyl, tridecanoyl, tetradecanoyl, hexadecanoyl, octadecanoyl, iso-butanoyl, t-butanoyl, cyclohexanecarbonyl, oleoyl Examples include oil, benzoyl, naphthylcarbonyl, and cinnamoyl groups. Among these, propionyl, butanoyl, dodecanoyl, octadecanoyl, t-butanoyl, oleoyl, benzoyl, naphthylcarbonyl, cinnamoyl and the like.
  As described above, cellulose acylates having different substituents can be obtained by appropriately adjusting the type and amount of carboxylic acid added when acylating cellulose.
  The preferred degree of substitution at the 6-position can be achieved by adjusting the aging time during the acetylation reaction as described above.
[0021]
The degree of polymerization of the cellulose acylate preferably used in the present invention is preferably from 280 to 380, more preferably from 285 to 350, and still more preferably from 290 to 330.
The molecular weight can be adjusted by extracting a low molecular weight component from the polymerized product or by improving the polymerization method. The removal of the low molecular component can be carried out by washing the cellulose acylate with an appropriate organic solvent. Moreover, when manufacturing a cellulose acylate with few low molecular components, it is preferable to adjust the sulfuric acid catalyst amount in an acetylation reaction to 0.5-25 mass parts with respect to 100 mass of cellulose. When the amount of the sulfuric acid catalyst is within the above range, cellulose acylate that is preferable in terms of molecular weight distribution (uniform molecular weight distribution) can be synthesized.
[0022]
2. Cellulose acylate film
Cellulose acylate film is cast on a drum or band with a high-concentration raw material dissolved in an organic solvent (dope) on a mirror surface and dried to form a film (solution casting method) .
In the cellulose acylate solution of the present invention, various additives (for example, plasticizers, ultraviolet inhibitors, deterioration inhibitors, optical anisotropy control agents, fine particles, release agents, infrared rays) according to the use in each preparation step. Absorbents, etc.) can be added and they can be solid or oily. That is, the melting point and boiling point are not particularly limited. For example, mixing of UV absorbing materials at 20 ° C. or lower and 20 ° C. or higher, and similarly mixing of a plasticizer is described in, for example, JP-A-2001-151901. Furthermore, infrared absorbing dyes are described, for example, in JP-A No. 2001-194522. Moreover, the addition time may be added at any time in the dope preparation step, but may be added by adding an additive to the final preparation step of the dope preparation step. Furthermore, the amount of each material added is not particularly limited as long as the function is manifested. Moreover, when a cellulose acylate film is formed from a multilayer, the kind and addition amount of the additive of each layer may differ. For example, it is described in Japanese Patent Application Laid-Open No. 2001-151902 and the like, but these are conventionally known techniques.
Furthermore, for these details, materials described in detail on pages 16 to 22 in the Japan Institute of Invention Disclosure Bulletin (Public Technical Number 2001-1745, published on March 15, 2001, Japan Institute of Invention) are preferably used.
[0023]
2-1: Solvent
As the organic solvent in which the cellulose acylate of the present invention is dissolved, both chlorinated solvents (dichloromethane, chloroform, etc.) and non-chlorinated solvents can be used. In the present invention, non-chlorinated solvents are more preferably used. That is, when used for a polarizing plate, a non-chlorine solvent is more preferable because it causes less fading when wet with heat. This is presumed to be because a trace amount of chlorinated solvent remaining in the cellulose acylate film diffuses into the polarizing layer, acts on PVA and iodine, and promotes fading.
[0024]
2-1-1 Non-chlorine solvent
The non-chlorine organic solvent preferably used in preparing the cellulose acylate solution of the present invention is preferably a solvent selected from esters, ketones and ethers having 3 to 12 carbon atoms. The ester, ketone and ether may have a cyclic structure. A compound having two or more functional groups of esters, ketones and ethers (that is, —O—, —CO— and —COO—) can also be used as a main solvent, such as an alcoholic hydroxyl group. It may have a functional group of In the case of the main solvent having two or more kinds of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group. Examples of esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate. Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone and methylcyclohexanone. Examples of ethers having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole. Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.
[0025]
The non-chlorine organic solvent used in the above cellulose acylate is selected from the various viewpoints described above, and is preferably as follows. That is, a preferred solvent for the cellulose acylate of the present invention is a mixed solvent of three or more different from each other, and the first solvent is selected from methyl acetate, ethyl acetate, methyl formate, ethyl formate, acetone, dioxolane, and dioxane. And at least one kind or a mixture thereof, the second solvent is selected from ketones having 4 to 7 carbon atoms or acetoacetate, and the third solvent is alcohol or hydrocarbon having 1 to 10 carbon atoms More preferably, it is a C1-C8 alcohol. Note that when the first solvent is a mixed liquid of two or more kinds of solvents, the second solvent may be omitted. The first solvent is more preferably methyl acetate, acetone, methyl formate, ethyl formate, or a mixture thereof, and the second solvent is preferably methyl ethyl ketone, cyclopentanone, cyclohexanone, or methyl acetyl acetate. It may be.
[0026]
The alcohol as the third solvent may be linear, branched or cyclic, and is preferably a saturated aliphatic hydrocarbon. The hydroxyl group of the alcohol may be any of primary to tertiary. Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, 1-pentanol, 2-methyl-2-butanol and cyclohexanol. As the alcohol, fluorine-based alcohol is also used. Examples thereof include 2-fluoroethanol, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol and the like. Furthermore, the hydrocarbon may be linear, branched or cyclic. Either aromatic hydrocarbons or aliphatic hydrocarbons can be used. The aliphatic hydrocarbon may be saturated or unsaturated. Examples of hydrocarbons include cyclohexane, hexane, benzene, toluene and xylene. These alcohols and hydrocarbons as the third solvent may be used alone or in combination of two or more, and are not particularly limited. Preferable specific examples of the third solvent include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and cyclohexanol, cyclohexane, hexanol, and particularly methanol, ethanol, 1-propanol, 2-propanol, 1-butanol.
[0027]
The above three types of mixed solvents preferably contain a first solvent in a proportion of 20 to 95% by mass, a second solvent in a proportion of 2 to 60% by mass, and a third solvent in a proportion of 2 to 30% by mass, Furthermore, it is preferable that a 1st solvent is 30-90 mass%, a 2nd solvent is 3-50 mass%, and also 3-25 mass% of 3rd alcohol is contained. Moreover, it is especially preferable that the 1st solvent is 30-90 mass%, the 2nd solvent is 3-30 mass%, the 3rd solvent is alcohol, and 3-15 mass% is contained. In addition, when the first solvent is a mixed solution and the second solvent is not used, the first solvent is preferably contained in a ratio of 20 to 95% by mass and the third solvent in a ratio of 80 to 5% by mass, More preferably, the first solvent is 30 to 93% by mass, and the third solvent is 70 to 7% by mass. The non-chlorine organic solvent used in the present invention is described in more detail in pages 12 to 16 in the Japan Society for Invention and Technology (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society for Invention). It is described in detail. Preferred combinations of non-chlorine organic solvents of the present invention can include the following, but are not limited thereto.
[0028]
-Methyl acetate / acetone / methanol / ethanol / butanol (75/10/5/5/5, parts by mass),
-Methyl acetate / acetone / methanol / ethanol / propanol (75/10/5/5/5, parts by mass),
Methyl acetate / acetone / methanol / butanol / cyclohexane (75/10/5/5/5, parts by mass),
Methyl acetate / methyl ethyl ketone / methanol / butanol (80/10/5/5, parts by mass),
-Methyl acetate / acetone / methyl ethyl ketone / ethanol / isopropanol (75/10/10/5/7, parts by mass)
Methyl acetate / cyclopentanone / methanol / isopropanol (80/10/5/8, parts by mass),
・ Methyl acetate / acetone / butanol (85/5/5, part by mass),
Methyl acetate / cyclopentanone / acetone / methanol / butanol (60/15/15/5/6, parts by mass),
-Methyl acetate / cyclohexanone / methanol / hexane (70/20/5/5, parts by mass)
Methyl acetate / methyl ethyl ketone / acetone / methanol / ethanol (50/20/20/5/5, parts by mass),
Methyl acetate / 1, 3 dioxolane / methanol / ethanol (70/20/5/5, parts by mass),
Methyl acetate / dioxane / acetone / methanol / ethanol (60/20/10/5/5, parts by mass),
Methyl acetate / acetone / cyclopentanone / ethanol / isobutanol / cyclohexane (65/10/10/5/5/5, parts by mass),
Methyl formate / methyl ethyl ketone / acetone / methanol / ethanol (50/20/20/5/5, parts by mass),
-Methyl formate / acetone / ethyl acetate / ethanol / butanol / hexane (65/10/10/5/5/5, parts by mass)
Acetone / methyl acetoacetate / methanol / ethanol (65/20/10/5, parts by mass)
Acetone / cyclopentanone / ethanol / butanol (65/20/10/5, parts by mass)
Acetone / 1,3 dioxolane / ethanol / butanol (65/20/10/5, part by mass),
1,3 dioxolane / cyclohexanone / methyl ethyl ketone / methanol / butanol (55/20/10/5/5/5, parts by mass)
Etc.
In addition to the above non-chlorine organic solvent, the dope may contain 10% by mass or less of dichloromethane based on the total amount of organic solvent.
[0029]
2-1-2: Chlorinated solvent
In preparing the cellulose acylate solution of the present invention, a chlorinated organic solvent may also be used. As described above, the fading property of the polarizing plate is likely to be lowered, but since cellulose acylate can be dissolved at a higher concentration, the drying process after casting can be shortened and the process cost can be reduced.
In the present invention, the chlorinated organic solvent is not particularly limited as long as the object can be achieved within a range in which cellulose acylate can be dissolved and cast and formed. These chlorinated organic solvents are preferably dichloromethane and chloroform. Particularly preferred is dichloromethane. In addition, there is no particular problem in mixing an organic solvent other than the chlorinated organic solvent. In that case, it is necessary to use at least 50% by mass of dichloromethane. The non-chlorine organic solvent used in combination with the present invention is described below. That is, as a preferable non-chlorine organic solvent, a solvent selected from esters, ketones, ethers, alcohols, hydrocarbons and the like having 3 to 12 carbon atoms is preferable. Esters, ketones, ethers and alcohols may have a cyclic structure. A compound having two or more functional groups of esters, ketones and ethers (that is, —O—, —CO— and —COO—) can also be used as a solvent. For example, other functional groups such as alcoholic hydroxyl groups can be used. You may have group simultaneously. In the case of a solvent having two or more types of functional groups, the number of carbon atoms may be within the specified range of the compound having any functional group. Examples of esters having 3 to 12 carbon atoms include ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate and pentyl acetate. Examples of ketones having 3 to 12 carbon atoms include acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone and methylcyclohexanone. Examples of ethers having 3 to 12 carbon atoms include diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole and phenetole. Examples of the organic solvent having two or more kinds of functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol and 2-butoxyethanol.
[0030]
The alcohol used in combination with the chlorinated organic solvent may be linear, branched or cyclic, and among them, saturated aliphatic hydrocarbon is preferable. The hydroxyl group of the alcohol may be any of primary to tertiary. Examples of the alcohol include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, 1-pentanol, 2-methyl-2-butanol and cyclohexanol. As the alcohol, fluorine-based alcohol is also used. Examples thereof include 2-fluoroethanol, 2,2,2-trifluoroethanol, 2,2,3,3-tetrafluoro-1-propanol and the like. Furthermore, the hydrocarbon may be linear, branched or cyclic. Either aromatic hydrocarbons or aliphatic hydrocarbons can be used. The aliphatic hydrocarbon may be saturated or unsaturated. Examples of hydrocarbons include cyclohexane, hexane, benzene, toluene and xylene.
[0031]
The chlorine-free organic solvent used in combination with the chlorine-based organic solvent that is the main solvent used in the cellulose acylate is not particularly limited, but methyl acetate, ethyl acetate, methyl formate, ethyl formate, acetone, dioxolane, dioxane , Ketones having 4 to 7 carbon atoms or acetoacetic acid esters, alcohols having 1 to 10 carbon atoms and hydrocarbons. Preferred non-chlorine organic solvents used in combination are methyl acetate, acetone, methyl formate, ethyl formate, methyl ethyl ketone, cyclopentanone, cyclohexanone, methyl acetyl acetate, methanol, ethanol, 1-propanol, 2-propanol, 1- Mention may be made of butanol, 2-butanol, and cyclohexanol, cyclohexane, hexane. Although the following can be mentioned as a combination of the chlorinated organic solvent which is a preferable main solvent of this invention, It is not limited to these.
[0032]
Dichloromethane / methanol / ethanol / butanol (75/10/5/5/5, parts by mass),
Dichloromethane / acetone / methanol / propanol (80/10/5/5, parts by mass),
Dichloromethane / methanol / butanol / cyclohexane (75/10/5/5/5, parts by mass),
Dichloromethane / methyl ethyl ketone / methanol / butanol (80/10/5/5, parts by mass),
Dichloromethane / acetone / methyl ethyl ketone / ethanol / isopropanol (75/10/10/5/7, parts by mass),
Dichloromethane / cyclopentanone / methanol / isopropanol (80/10/5/8, parts by mass)
Dichloromethane / methyl acetate / butanol (80/10/10, parts by mass),
Dichloromethane / cyclohexanone / methanol / hexane (70/20/5/5, parts by mass)
Dichloromethane / methyl ethyl ketone / acetone / methanol / ethanol (50/20/20/5/5, parts by mass),
Dichloromethane / 1, 3 dioxolane / methanol / ethanol (70/20/5/5, parts by mass),
Dichloromethane / dioxane / acetone / methanol / ethanol (60/20/10/5/5, parts by mass),
Dichloromethane / acetone / cyclopentanone / ethanol / isobutanol / cyclohexane (65/10/10/5/5/5, parts by mass),
Dichloromethane / methyl ethyl ketone / acetone / methanol / ethanol (70/10/10/5/5, parts by mass),
Dichloromethane / acetone / ethyl acetate / ethanol / butanol / hexane (65/10/10/5/5/5, parts by mass),
Dichloromethane / methyl acetoacetate / methanol / ethanol (65/20/10/5, parts by mass),
Dichloromethane / cyclopentanone / ethanol / butanol (65/20/10/5, parts by mass),
Etc.
[0033]
2-2: Additive
Various additives according to the application can be added to the cellulose acylate solution in each preparation step. These additives are plasticizers, UV inhibitors and deterioration inhibitors (eg, antioxidants, peroxide decomposers, radical inhibitors, metal deactivators, acid scavengers, amines). Preferred plasticizers to be added include triphenyl phosphate (TPP), diphenyl biphenyl phosphate, tricresyl phosphate (TCP), dioctyl phthalate (DOP), tributyl O-acetylcitrate (OACTB), acetyl triethyl citrate, As a plasticizer for reducing optical anisotropy, (di) pentaerythritol esters described in JP-A No. 11-124445, glycerol esters described in JP-A No. 11-246704, JP-A No. 2000-63560 The diglycerol esters described in the gazette, the citrate esters described in JP-A No. 11-92574, the substituted phenyl phosphate esters described in JP-A No. 11-90946 are preferably used. These plasticizers may be used alone or in combination of two or more. The addition amount of the plasticizer is preferably 5 to 30% by mass, particularly preferably 8 to 16% by mass with respect to the cellulose acylate.
[0034]
As for the deterioration preventing agent and the ultraviolet ray preventing agent, JP-A-60-235852, JP-A-3-199201, JP-A-51907073, JP-A-5-194789, JP-A-5-271471, JP-A-6-107854, 6-118233, 6-148430, 7-11056, 7-11055, 7-11056, 8-29619, 8-239509 and JP-A-2000-204173. There is a description.
Examples of the deterioration preventing agent include butylated hydroxytoluene (BHT).
The ultraviolet absorber is preferably one that has an excellent ability to absorb ultraviolet light having a wavelength of 370 nm or less and has little absorption of visible light having a wavelength of 400 nm or more. An oxybenzophenone compound, a benzotriazole compound, a salicylic acid ester compound, a benzophenone compound, Examples thereof include cyanoacrylate compounds and nickel complex compounds, and benzotriazole compounds and benzophenone compounds are particularly preferable. Examples of the ultraviolet absorber include those disclosed in JP-A-6-148430, JP-A-7-11056, JP-A-8-239509, JP-A-10-237186, JP-A-2001-72782, and JP-A-2002-79533. Those described in each publication can be used.
The amount of these compounds added is preferably 1 ppm to 10,000 ppm and more preferably 10 to 1000 ppm in terms of mass ratio with respect to cellulose acylate.
[0035]
The in-plane retardation (Re) of the film is preferably in the range of 0 to 300 nm and is adjusted according to the application. In addition, retardation (Rth) in the thickness direction of the film is also important, and Rth of cellulose acylate film is 0 nm to 600 nm per 100 μm, more preferably 0 nm to 400 nm, and particularly 0 nm to 250 nm. It is done.
Further, a release agent can be added in order to reduce the peeling stress from the band and drum during film formation. As the release agent, one selected from at least one acid having an acid dissociation index pKa in an aqueous solution of 1.93 to 4.50, an alkali metal salt of the acid and an alkaline earth metal salt of the acid is preferably used. It is done.
[0036]
2-3: Dissolution
The cellulose acylate of the present invention is preferably a solution in which 10 to 30% by mass is dissolved in an organic solvent, more preferably 13 to 27% by mass, and particularly preferably 15 to 25% by mass. An acylate solution.
Regarding the preparation of the cellulose acylate solution (dope) of the present invention, the dissolution method is not particularly limited, and it may be room temperature, or a cooling dissolution method or a high temperature dissolution method, or a combination thereof. Regarding these, for example, JP-A-5-163301, JP-A-61-106628, JP-A-58-127737, JP-A-9-95544, JP-A-10-95854, JP-A-10-45950, JP 2000-53784, JP 11-322946, JP 11-322947, JP 2-276830, JP 2000-273239, JP 11-71463, JP 04-259511, Special JP-A 2000-273184, JP-A No. 11-323017, JP-A No. 11-302388 and the like disclose methods for preparing a cellulose acylate solution.
The above-described method for dissolving cellulose acylate in an organic solvent can be applied to the present invention as long as it is within the scope of the present invention. These details are described in detail on pages 22 to 25 in the Japan Society for Invention and Technology (Publication No. 2001-1745, published on March 15, 2001, Japan Society for Inventions), especially for non-chlorine solvent systems. Can be implemented in any way.
Further, the cellulose acylate dope solution of the present invention is usually subjected to solution concentration and filtration, and similarly, page 25 of the Japan Society for Invention and Technology (Publication No. 2001-1745, published on March 15, 2001, Japan Society of Inventions). Are described in detail. In addition, when it melt | dissolves at high temperature, it is the case where it is more than the boiling point of the organic solvent to be used, and in that case, it uses in a pressurized state.
[0037]
The cellulose acylate solution of the present invention preferably has a viscosity and dynamic storage modulus within the range. 1 mL of the sample solution was measured with a rheometer (CLS 500) using a Steel Cone having a diameter of 4 cm / 2 ° (both manufactured by TA Instruments). Measurement conditions were measured using an Oscillation Step / Temperature Ramp with a range of 40 ° C. to −10 ° C. being varied at 2 ° C./min, static non-Newtonian viscosity n * (Pa · s) at 40 ° C. and storage at −5 ° C. The elastic modulus G ′ (Pa) is obtained. The measurement was started after the sample solution was kept warm at the measurement start temperature until the liquid temperature became constant. In the present invention, the viscosity at 40 ° C. is 1 to 300 Pa · s, and the dynamic storage elastic modulus at −5 ° C. is 10,000 to 1,000,000 Pa.
[0038]
2-4: Casting film formation
A method for producing a film using the cellulose acylate solution of the present invention will be described. For the method and equipment for producing the cellulose acylate film of the present invention, a solution casting film forming method and a solution casting film forming apparatus conventionally used for producing a cellulose triacetate film are used. The dope (cellulose acylate solution) prepared from the dissolving machine (kettle) is temporarily stored in a storage kettle, and the foam contained in the dope is defoamed for final preparation. The dope is sent from the dope discharge port to the pressure die through a pressure metering gear pump capable of delivering a constant amount of liquid with high accuracy, for example, by the number of rotations, and the dope is run endlessly from the die (slit) of the pressure die. The dry-dried dope film (also referred to as web) is peeled off from the metal support at a peeling point that is uniformly cast on the metal support and substantially rounds the metal support. Both ends of the obtained web are sandwiched between clips, transported by a tenter while keeping the width, dried, then transported by a roll group of a drying device, dried, and wound up to a predetermined length by a winder. The combination of the tenter and the roll group dryer varies depending on the purpose. In the solution casting film forming method used for silver halide photographic light-sensitive materials and functional protective films for electronic displays, in addition to the solution casting film forming apparatus, an undercoat layer, an antistatic layer, an antihalation layer, a protective layer, etc. In many cases, a coating device is added to the surface processing of the film. Each of these manufacturing processes is described in detail on pages 25 to 30 of the Japan Society of Invention Disclosure Technical Report (Public Technical Number 2001-1745, published on March 15, 2001, Japan Society of Invention). ), Metal support, drying, peeling, stretching, etc.
[0039]
Here, although the space temperature of a casting part is not specifically limited in this invention, It is preferable that it is -50-50 degreeC. Furthermore, it is preferable that it is -30-40 degreeC, and it is especially preferable that it is -20-30 degreeC. In particular, the cellulose acylate solution cast at a low space temperature can be cooled on the support instantly to increase the gel strength, thereby holding the film containing the organic solvent. Thereby, it is possible to peel off from the support in a short time without evaporating the organic solvent from the cellulose acylate, and high-speed casting can be achieved. The means for cooling the space may be normal air, nitrogen, argon, helium or the like, and is not particularly limited. The humidity in that case is preferably 0 to 70% RH, and more preferably 0 to 50% RH. Moreover, in this invention, the temperature of the support body of the casting part which casts a cellulose acylate solution is -50-130 degreeC, Preferably it is -30-25 degreeC, Furthermore, it is -20-15 degreeC. In order to keep the casting part at the temperature of the present invention, it may be achieved by introducing a cooled gas into the casting part, or a cooling device may be arranged in the casting part to cool the space. At this time, it is important to take care not to attach water, and it can be carried out by a method such as using dry gas.
[0040]
In the present invention, the following configurations are particularly preferred for the contents and casting of each layer. That is, the cellulose acylate solution is a cellulose acylate solution containing 0.1 to 20% by mass of at least one liquid or solid plasticizer with respect to cellulose acylate at 25 ° C. and / or at least It is a cellulose acylate solution containing 0.001 to 5% by mass of one kind of liquid or solid UV absorber with respect to cellulose acylate, and / or an average particle size of 5 to 5 of at least one kind of solid. It is a cellulose acylate solution containing 0.001 to 5% by mass of fine particle powder of 3000 nm with respect to cellulose acylate, and / or at least one fluorosurfactant with respect to cellulose acylate A cellulose acylate solution containing 0.001 to 2% by mass and / or a small amount Both are cellulose acylate solutions containing 0.0001 to 2% by mass of one type of release agent with respect to cellulose acylate, and / or at least one type of deterioration inhibitor is 0.0001 with respect to cellulose acylate. A cellulose acylate solution containing ˜2 mass%, and / or containing 0.1-15 mass% of at least one optical anisotropy control agent with respect to cellulose acylate, and / or Or the cellulose acylate solution which contains 0.1-5 mass% of at least 1 type of infrared absorber with respect to a cellulose acylate, and the cellulose acylate film produced from it are preferable.
[0041]
In the casting step, one type of cellulose acylate solution may be cast as a single layer, or two or more types of cellulose acylate solutions may be cast simultaneously and / or sequentially. In the case of having a casting process comprising two or more layers, the composition and concentration of the solvent in each layer in the produced cellulose acylate solution and cellulose acylate film may be the same or different. The number of layers is preferably 2 to 10, more preferably 3 to 5. Although the thickness of these layers can be selected arbitrarily, the thickness of the outermost layer is preferably 0.01 to 0.3 times or less, more preferably 0.05 to 0.15 times the thickness of the innermost layer.
[0042]
3. Saponification treatment
In order to improve the adhesiveness with the PVA forming the polarizing plate, the surface is saponified by the above-described method, and the cellulose acylate is hydrolyzed to generate a hydroxyl group. Following this, sufficient water washing is performed by the above-described method.
[0043]
4). Creating a polarizing plate
4-1: Binder for polarizing layer
The polarizing layer is prepared by orienting a polarizing dye dispersed in PVA in one direction. PVA is usually a saponified polyvinyl acetate, and may contain components copolymerizable with vinyl acetate such as unsaturated carboxylic acids, unsaturated sulfonic acids, olefins, and vinyl ethers. In addition, modified PVA containing an acetoacetyl group, a sulfonic acid group, a carboxyl group, an oxyalkylene group, or the like can also be used.
Although the saponification degree of PVA is not specifically limited, 80-100 mol% is preferable from viewpoints of solubility etc., and 90-100 mol% is especially preferable. The degree of polymerization of PVA is not particularly limited, but is preferably 1000 to 10,000, and particularly preferably 1500 to 5000.
[0044]
4-2: Dyeing
A polarizing film is obtained by dyeing PVA with iodine. That is, it is carried out by immersing the PVA film in an iodine-potassium iodide aqueous solution. Iodine is preferably 0.1 to 20 g / l, potassium iodide is preferably 1 to 200 g / l, and the mass ratio of iodine and potassium iodide is preferably 1 to 200. The dyeing time is preferably 10 to 5000 seconds, and the liquid temperature is preferably 5 to 60 ° C. As a dyeing method, not only immersion but any means such as application or spraying of iodine or a dye solution can be used. The dyeing step may be placed either before or after the stretching step of the present invention, but it is particularly preferable to dye in the liquid phase before the stretching step because the film is appropriately swelled to facilitate stretching.
The effect of the present invention is similarly exhibited in a polarizing film stained with other than iodine. This is because the present invention does not improve the resistance of the dye but improves boric acid, which is a PVA crosslinking agent fixing the dye. Examples of preferable dyes other than iodine include dye compounds such as azo dyes, stilbene dyes, pyrazolone dyes, triphenylmethane dyes, quinoline dyes, oxazine dyes, thiazine dyes, anthraquinone dyes, and the like. Can be mentioned.
[0045]
4-3: Dura mater
In order to fix the oriented structure of PVA after stretching, it is preferable to crosslink PVA. As the crosslinking agent, those described in US Pat. No. 2,328,977 can be used, but boric acid and borax are preferably used practically. In addition, metal salts such as zinc, cobalt, zirconium, iron, nickel, and manganese can be used together.
Such a film can be achieved by immersing PVA impregnated with a dye in an aqueous solution of borax or boric acid. The content of borax and boric acid is preferably 0.1 to 10 mol / l, more preferably 0.2 to 5 mol / l, still more preferably 0.2 to 2 mol / l. The liquid temperature is preferably 10 ° C. to 40 ° C., more preferably 15 ° C. to 35 ° C. The immersion time is 10 seconds or longer and 10 minutes or shorter, more preferably 20 seconds or longer and 5 minutes or shorter. It is also preferable to put iodide salts such as sodium iodide and potassium iodide in the dura mater. This concentration is preferably from 0.1 to 10 mol / l, more preferably from 0.2 to 5 mol / l, still more preferably from 0.2 to 2 mol / l.
Such hardening may be performed anywhere before stretching, during stretching, or after stretching.
[0046]
4-4: Stretching
A PVA film impregnated with a dye or the like is stretched and oriented. The stretching may be performed in parallel to the transport direction, may be performed in the orthogonal direction, or may be performed in an oblique direction. Among these, a parallel direction (parallel stretching method) and a 45-degree oblique direction (oblique stretching method) are preferable. This is because the obliquely stretched polarizing film is more excellent in fading. The reason for this is estimated as follows. That is, since the parallel stretching is mainly performed by two pairs of nip rolls, neck-in occurs during stretching, and the width becomes narrow. On the other hand, oblique stretching cannot be necked in because it is stretched by a tenter. As a result, since it decreases in the thickness direction as much as it cannot be contracted in the width direction, the plane orientation proceeds. Such a plane-oriented polarizing layer has a solid alignment structure, is not easily disturbed even by a wet heat thermometer, and is presumed to have high thermo resistance.
The thickness of the polarizing layer after stretching is preferably 5 μm or more and 50 μm or less, and more preferably 10 μm or more and 40 μm or less in any stretching method.
[0047]
Hereinafter, each stretching method will be described slightly.
(I) Parallel stretching method
Prior to stretching, the PVA film is swollen. The degree of swelling is 1.2 to 2.0 times (mass ratio before swelling and after swelling). Thereafter, the film is stretched at a bath temperature of 15 to 50 ° C., particularly 17 to 40 ° C. in an aqueous medium bath or a dye bath for dissolving a dichroic substance while being continuously conveyed through a guide roll or the like. Stretching can be achieved by gripping with two pairs of nip rolls and increasing the conveyance speed of the subsequent nip roll to be higher than that of the previous nip roll. The draw ratio is based on the length ratio after stretching / initial state (hereinafter the same), but the preferred draw ratio is 1.2 to 3.5 times, especially 1.5 to 3.0 times from the viewpoint of the above-mentioned effects. is there.
Thereafter, the film is dried at 50 ° C. to 90 ° C. to obtain a polarizing film.
[0048]
(Ii) Diagonal stretching method
As this method, for example, a method of stretching using a tenter projecting in an oblique direction described in JP-A-2002-86554 can be mentioned.
Since this stretching is performed in the air, it is necessary to make it easy to stretch by adding water in advance. A preferable moisture content is 5% or more. This includes immersing, coating and spraying before stretching, and applying water or the like during stretching. Since hydrophilic polymer films such as polyvinyl alcohol contain water in a high-temperature and high-humidity atmosphere, they can contain volatile components by stretching after conditioning in a high-humidity atmosphere or by stretching under high-humidity conditions. . Other than these methods, any means may be used as long as the moisture content of the polymer film can be increased to 5% or more. More preferably, it is 10% or more and 100% or less.
The temperature during stretching is preferably 40 ° C. or higher and 90 ° C. or lower, and more preferably 50 ° C. or higher and 80 ° C. or lower. The humidity is preferably 50% RH to 100% RH, more preferably 70% RH to 100% RH, and still more preferably 80% RH to 100% RH.
Further, the traveling speed in the longitudinal direction is preferably 1 m / min or more, more preferably 3 m / min or more.
After the end of stretching, the temperature is from 50 ° C. to 100 ° C., more preferably from 60 ° C. to 90 ° C., and from 0.5 minutes to 10 minutes, more preferably from 1 minute to 5 minutes.
The polarizing film thus obtained is preferably substantially 45 degrees in the transport direction, and substantially 45 degrees means 45 ± 5 degrees.
[0049]
4-5: Bonding
The saponified cellulose acylate film and a polarizing layer prepared by stretching are bonded to prepare a polarizing plate. The laminating direction is preferably such that the casting axis direction of the cellulose acylate film and the stretching axis direction of the polarizing plate are 45 degrees. The adhesive for bonding is not particularly limited, and examples thereof include PVA resins (including modified PVA such as acetoacetyl group, sulfonic acid group, carboxyl group, oxyalkylene group) and boron compound aqueous solution. Is preferred. The thickness of the adhesive layer is preferably 0.01 to 10 μm after drying, and particularly preferably 0.05 to 5 μm.
[0050]
5. Application of polarizing plate
5-1: Circularly polarizing plate
The polarizing plate and the λ / 4 plate thus obtained can be laminated to create circularly polarized light. In this case, lamination is performed so that the slow axis of λ / 4 and the absorption axis of the polarizing plate are 45 degrees. At this time, λ / 4 is not particularly limited, but more preferably has a wavelength dependency such that the lower the wavelength, the smaller the retardation. Furthermore, it is preferable to use a polarizing film having an absorption axis inclined by 20 to 70 degrees with respect to the longitudinal direction and a λ / 4 plate made of an optically anisotropic layer made of a liquid crystalline compound.
[0051]
5-2: Liquid crystal display element
When used in a reflective liquid crystal display device, in order from the bottom, it consists of a lower substrate, a reflective electrode, a lower alignment film, a liquid crystal layer, an upper alignment film, a transparent electrode, an upper substrate, a λ / 4 plate, and a polarizing plate. The polarizing plate of the present invention can be used. In the case of color display, it is preferable to further provide a color filter layer between the reflective electrode and the lower alignment film, or between the upper alignment film and the transparent electrode.
When used in a transmissive liquid crystal display device, the backlight, polarizing plate, λ / 4 plate, lower transparent electrode, lower alignment film, liquid crystal layer, upper alignment film, upper transparent electrode, upper substrate, λ / 4 are sequentially arranged from the bottom. It consists of a plate and a polarizing film. The thing of this invention can be used for the polarizing plate in this. In the case of color display, it is preferable to further provide a color filter layer between the lower transparent electrode and the lower alignment film, or between the upper alignment film and the transparent electrode.
The liquid crystal cell is not particularly limited, but more preferably a TN (twisted nematic) type, STN (supplier twisted nematic) type or HAN (hybrid aligned nematic) type, VA (verticaly allignment) type, ECB type (electrically controlled birefrigence), OCB A type (Optically Compensatory Bend) and a CPA type (Continious Pinwheel Alignment) are preferable.
[0052]
The measurement methods used in the present invention are described below.
(1) Content of boron in the polarizing layer
(I) Wet ashing
Stick a polarizing plate on a glass plate, 2cm²Expose and mask the rest with Mylar adhesive tape. Chloroform is added dropwise thereto to swell the cellulose acylate film and scrape it off. Thereafter, the polarizing layer is scraped off. To this, 2 ml of nitric acid is added to make multiwave ashing (ashing by microwave). This is made up to 100 ml with pure water, and then diluted 100 times.
(Ii) ICP-MS measurement
The amount of boron is quantified using ICP-MS (HP-4500 manufactured by Yokogawa Analytical). Measure this on the samples before and after the wet heat thermometer and compare the measured intensity.
[0053]
(2) NMR of boron in the polarizing layer
(I) Sample preparation
A polarizing plate is stretched on a glass plate, chloroform is dropped on a cellulose acylate film on one side, swollen, and then peeled off. Thereafter, the polarizing layer is taken out.
(Ii) NMR measurement
The sample (polarizing layer) is cut into a strip and inserted into a 7 mmφ rotor for solid-state NMR measurement. This is measured using the NMR apparatus (AVANCE-300WB manufactured by Bruker) under the following conditions.
・ Measurement method: 1 pulse + 1H decoupling method
・ Magnetic field: 7.1T
・ Resonance frequency: 96.3 MHz
Reference material: Saturated H_ThreeBO_ThreeThe aqueous solution was measured at 23 ° C. without applying MAS, and this was 19.5 ppm (external standard method)
・ Magic angle rotation speed: 3000Hz
・ Pulse repetition time: 3 seconds
・ Measurement width: 50 kHz
Data acquisition point: 2048
・ Pulse flip angle: 45 degrees
[0054]
(3) Degree of substitution of cellulose acylate
The acyl substitution degree at the 2-position, 3-position and 6-position of cellulose acylate is described in Carbohydr. Res. 273 (1995) 83-91 (Tezuka et al.)¹³Obtained by C-NMR.
(4) Degree of polymerization of cellulose acylate (DP)
-About 0.2 g of completely dried cellulose acylate was precisely weighed and dissolved in 100 ml of a mixed solvent of methylene chloride: ethanol = 9: 1 (mass ratio). This was measured for the number of seconds dropped at 25 ° C. with an Ostwald viscometer, and the degree of polymerization (DP) was determined by the following formula.
Formula: DP = [η] / 6 × 10^-Four
Here, [η] = (1nη_rel) / C, where C is the measured concentration (g / L).
In addition, the above η_relIs a value calculated by T / T0, T is the number of seconds dropped for the measurement sample, and T0 is the number of seconds dropped for the solvent alone.
[0055]
【Example】
EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.
[0056]
1. Cellulose acylate film production
1-1: Cellulose acylate
The substituted acyl groups described in Table 1 and cellulose acylates having different degrees of polymerization were prepared. This was carried out by adding sulfuric acid (7.8 parts by mass with respect to 100 parts by mass of cellulose) as a catalyst, adding carboxylic acid as a raw material for the acyl substituent, and carrying out an acylation reaction at 40 ° C. At this time, the kind and substitution degree of the acyl group shown in Table 1 were adjusted by adjusting the kind and amount of the carboxylic acid. Further, aging was carried out at 40 ° C. after acylation, and the substitution degree at the 6-position was adjusted by adjusting this time. Thereafter, the sample was precipitated with a large excess of water, washed with warm water at 60 ° C., and samples having different residual amounts of Mg and Ca were prepared by changing this time. The residual amounts of Mg and Ca were measured by the following method.
[0057]
<Method for quantifying Mg and Ca>
(I) Wet ashing
Cellulose acylate 20 mg is sampled, and 2 ml of nitric acid is added to make multiwave ash (ash by microwave).
After making up the volume to 100 ml with pure water, 5 pieces diluted 1000 times are prepared. To this, standard solutions of Mg and Ca are added so as to be 0, 10, 50, 100, and 200 ppb.
(Ii) ICP-MS measurement
Using ICP-MS (HP-4500 manufactured by Yokogawa Analytical), Mg and Ca in these samples are quantified. That is, the Ca, Mg addition concentration of the standard solution is taken on the horizontal axis, the detected amount is taken on the vertical axis, the plot is connected by the least square method, and the intercept is calculated from this vertical axis.
Furthermore, samples with different average degrees of polymerization were prepared by washing and removing low molecular weight components of the cellulose acylate with acetone.
[0058]
1-2: Dissolution of cellulose acylate
Cellulose acylate flakes were selected from the following solvents (described in Table 1) and charged to 23% by mass, followed by stirring.
Non-chlorine system: methyl acetate / acetone / methanol / ethanol / butanol (75/10/5/5/5, parts by mass)
Chlorine: dichloromethane / methanol / ethanol / butanol (75/10/5/5/5, parts by mass)
A plasticizer (triphenyl phosphate: diphenylbiphenyl phosphate = 2: 1 (mass ratio)) was added to this by 12 mass% with respect to cellulose acylate. Furthermore, 2 mass% of the total amount of the dope was added to the ultraviolet absorber (UV-9) described in Example 1 of JP-A-7-11056. The heterogeneous gel solution thus obtained was kneaded at −75 ° C. for 3 minutes. This was stirred at 50 ° C. for 2 hours to obtain a homogeneous solution, returned to room temperature, filtered through 10 μm filter paper (# 63, manufactured by Toyo Filter Paper Co., Ltd.), and further 2.5 μm filter paper (manufactured by Pall, FH025). To obtain a cellulose acylate dope.
[0059]
1-3: Film formation of cellulose triacetate film
The filtered cellulose triacetate dope at 50 ° C. was cast on a mirror surface stainless steel support, which is a drum having a diameter of 3 m, through a cast Gicer (the temperature of the support was set at −5 ° C.). The Gieseer used was similar to that described in Japanese Patent Application Laid-Open No. 11-314233. The casting speed was 75 m / min and the coating width was 200 cm. The temperature of the entire space of the casting part was set to 15 ° C. Then, the cellulose acylate film cast and rotated 50 cm before the cast part was peeled off from the drum, and both ends were clipped with a pin tenter. Thereafter, the cellulose acylate film held by the pin tenter was conveyed to the drying zone. First, drying was performed by blowing a 45 ° C. drying air. The film was further dried at 110 ° C. for 5 minutes and further at 145 ° C. for 10 minutes (film temperature was about 140 ° C.) to obtain a cellulose triacetate film (film thickness: 80 μm). The obtained sample was cut at 3 cm at both ends, and further knurled at a height of 100 μm at a portion 2 to 10 mm from the end, and wound into a 2000 m roll.
[0060]
[Table 1]

[0061]
1-4: Saponification of cellulose acylate film
Saponification was carried out by one of the following methods and listed in Table 1.
(I) Coating saponification
-20 parts by mass of water was added to 80 parts by mass of iso-propanol, and KOH was dissolved in 1.5 N, and the temperature was adjusted to 20 ° C. and used as a saponification solution.
-This was apply | coated on the cellulose acylate film of 20 degreeC, it processed for the time of Table 1, and the saponification depth was adjusted.
After this, washing was performed by the water washing method or neutralization method (described in Table 1).
Washing method: 10 l / m using 50 ° C hot water spray²・ Spray for 1 minute.
Neutralization method: Immerse in a 0.5N sulfuric acid bath at 25 ° C. for 30 seconds, and then immerse in a 25 ° C. water bath for 30 seconds.
(Ii) Immersion saponification
-A 1.5 N aqueous solution of NaOH was used as the saponification solution.
The temperature was adjusted to 25 ° C., and the cellulose acylate film was immersed for the time shown in Table 1 to adjust the saponification depth.
Thereafter, washing was performed by a water washing method or a neutralization method (described in Table 1) in the same manner as the coating saponification method.
[0062]
The saponification depth and the residual acid amount on the surface of the saponification sample thus obtained were measured by the following methods.
<Saponification depth measurement method>
-Using a microtome, a cellulose acylate film is sliced at an angle of 45 degrees and a section having a thickness of 2 μm is prepared.
This is measured using a microscopic IR every 2 μm from the surface with an aperture of 5 μm × 20 μm (the outermost surface is measured by combining the 20 μm side of the aperture and the outermost surface of the section).
・ 1700-1800cm^-1Absorbance (A1) and 1100-1000 cm^-1(A1 / A2) is obtained by taking the ratio of the maximum absorbance (A2) appearing in. A1 originates from the carbonyl group of the acyl group, and A2 originates from both the carbonyl group of the acyl group and the ether bond of the glucopyranose ring, meaning that saponification progressed as the ratio decreased.
・ Measurement depth on the horizontal axis (the depth of the measurement point of the X step from the surface is expressed as 2X / (sin 45 °), the outermost surface is X = 1), and A1 / A2 is taken on the vertical axis. Plot.
-The area | region where A1 / A2 is 1.5 or less was made into the saponification depth.
<Residual acid amount>
-The saponified surface was measured with XPS (ESCA-750, manufactured by Shimadzu Corporation), and the S2p signal due to the acid used for washing was measured.
A value obtained by dividing the area of this peak by the area of the peak of C and further dividing by the ionization cross-sectional area of the peak of S2p was used as the percentage of the remaining acid.
[0063]
2. Creating a polarizing plate
2-1: Creation of polarizing layer
A polarizing layer having a thickness of 20 μm was prepared by any of the following methods (described in Table 2).
(I) Diagonal stretching method
A PVA film (Kuraray 9X75SR) was immersed in a dyeing solution having the following composition at 25 ° C. for 90 seconds.
<Dyeing liquid>
1.0 parts by mass of iodine
Potassium iodide 60.0 parts by mass
1000 parts by weight of water
This was immersed for 120 seconds at 25 ° C. in any one of the following hardeners (described in Table 2) to prepare different boric acid initial contents.
<Hardener 1
40 parts by mass of boric acid
30 parts by mass of potassium iodide
1000 parts by weight of water
<Hardener 2
80 parts by mass of boric acid
60 parts by mass of potassium iodide
1000 parts by weight of water
<Hardener 3>
120 parts by mass of boric acid
90 parts by mass of potassium iodide
1000 parts by weight of water
Then, according to Example 1 of Unexamined-Japanese-Patent No. 2002-86554, it extended | stretched so that the extending | stretching axis might become 45 degrees diagonally using the tenter. In addition, extending | stretching was made to shrink | contract to 5.3 time after extending | stretching 7 time in 60 degreeC95% RH. Then, it was dried at 70 ° C. for 2 minutes.
[0064]
(Ii) Parallel stretching method
According to Example 1 of Japanese Patent Laid-Open No. 2001-141926, a PVA film (Kuraray 9X75SR) is immersed in the dyeing solution at 30 ° C., giving a peripheral speed difference between two pairs of nip rolls, and tripled in the longitudinal direction. Stretched.
This was further immersed in the above hardening solution and stretched at 60 ° C. using two pairs of nip rolls 6.5 times (magnification relative to the unstretched film). This was dried at 50 ° C. for 5 minutes.
[0065]
2-2: Bonding
The polarizing plate thus obtained and the saponified cellulose acylate film were bonded together using a 3% aqueous solution of PVA (PVA-117H manufactured by Kuraray Co., Ltd.) as an adhesive, and further heated at 60 ° C. for 30 minutes. A polarizing plate was created. Bonding was performed so that the polarization axis and the longitudinal direction of the cellulose acylate film were 45 degrees.
[0066]
3. Evaluation of polarizing plate
The polarizing plate was attached to both surfaces of the glass plate with an adhesive so that the polarization axes were perpendicular. This was aged for 1000 hours at 60 ° C. and 95% RH.
The total light transmittance of this was measured, and the polarization ability was evaluated. Further, the polarizing layer was taken out of the polarizing plate before and after the thermo treatment, and the boron content was measured by the above method. Further, from this ratio, the rate of change in the amount of boron accompanying the thermo treatment was determined. Further, the NMR of boron in the polarizing layer was measured from the polarizing plate after the thermo treatment by the above method, and the intensity ratio between 0 ppm and 10 ppm was determined. These values are listed in Table 2.
Also, the adhesiveness is 1000 hours thermo-treatment at 60 ° C and 95% RH, and 10 mm each is cut into the polarizing layer every 3 mm with a razor, and adhesive tape is attached to this, and this is quickly peeled off. The area (%) of the polarizing layer that was not removed and peeled off was visually evaluated. The results are shown in Table 2.
[0067]
[Table 2]

[0068]
The polarizing plate of the present invention achieves extremely robust durability, not to mention the 1000 hour thermo treatment at 60 ° C. and 95% RH, and to obtain good results even under the more severe conditions of 70 ° C. and 95% RH. It was.
In the polarizing plate of the present invention, the saponification depth of the cellulose acylate film was reduced in order to achieve the thermo durability, but good adhesiveness was achieved by reducing the Mg and Ca contents.
[0069]
4). Application of polarizing plates to display elements
An optical anisotropy comprising the polarizing plate of the present invention comprising a liquid crystal display device described in Example 1 of JP-A-10-48420 and a discotic liquid crystal molecule described in Example 1 of JP-A-9-26572. Layer, alignment film coated with polyvinyl alcohol, VA type liquid crystal display device described in FIGS. 2 to 9 of JP 2000-154261 A, OCB type liquid crystal display described in FIGS. 10 to 15 of JP 2000-154261 A When used in the apparatus, good performance was obtained.
[0070]
【The invention's effect】
According to the present invention, it is possible to provide a polarizing plate excellent in durability even under extremely severe wet heat conditions.

Claims (10)

A method for producing a polarizing plate comprising a cellulose acylate film and a polarizing layer containing polyvinyl alcohol, iodine and boric acid,
The cellulose acylate film was subjected to alkali saponification treatment, washed only with water, bonded to the polarizing layer, and after 1000 hours in an atmosphere of 60 ° C. and 95% RH, the boron content in the polarizing layer was 79 % of the initial value. The manufacturing method of the polarizing plate characterized by preparing the polarizing plate of 100% or less above. The polarized light according to claim 1, wherein the content of boron in the polarizing layer is 2 mmol / m ² · µm or more and 20 mmol / m ² · µm or less after 1000 hours in an atmosphere of 60 ° C and 95% RH. A manufacturing method of a board. The ratio of the peak intensity of 0 ppm to the peak of 12 ppm (peak height of 0 ppm / peak height of 12 ppm) is 2 or more when NMR measurement is performed on boron in the polarizing layer after 1000 hours in an atmosphere of 60 ° C. and 95% RH. It is 40 or less, The manufacturing method of the polarizing plate of Claim 1 or 2 characterized by the above-mentioned. The method for producing a polarizing plate according to any one of claims 1 to 3, wherein the washing is performed by spraying warm water of 40 ° C or higher in a spray form . The method for producing a polarizing plate according to claim 4, wherein the cellulose acylate film has a substitution degree of an acyl group substituted with a hydroxyl group at the 6-position of cellulose of 0.87 or more and 0.95 or less. The cellulose acylate film is at least selected from ethers having 3 to 12 carbon atoms, ketones having 3 to 12 carbon atoms, and esters having 3 to 12 carbon atoms, which are non-chlorine organic solvents. 6. The method for producing a polarizing plate according to claim 4, wherein the polarizing plate is formed by a solution casting method using a kind of solvent. The method for producing a polarizing plate according to claim 1, wherein the absorption axis of the polarizing layer is substantially 45 ° inclined and stretched by a tenter. The method for producing a polarizing plate according to any one of claims 1 to 7, wherein the water washing is performed so that the film surface pH is 5 to 9. The production of a polarizing plate according to any one of claims 1 to 8, wherein a saponification solution in which the alkali saponification treatment is adjusted to 10 to 30 ° C is used, and the reaction time is 1 second to 5 minutes. Method. The method for producing a polarizing plate according to claim 9, wherein the alkali saponification treatment is performed using a saponification solution adjusted to 10 to 25 ° C.